The invention relates to a method of corrugating metal tubes in which a smooth tube, preferably a longitudinal seam-welded smooth tube, is passed continuously through a bushing and the smooth tube is acted on directly behind the bushing by a corrugating tool in which a corrugator disk having a larger inside diameter than the diameter of the smooth tube is mounted for free rotation eccentrically in a corrugator head which can be driven in rotation.
From Federal Republic of Germany AS No. 1086314 a method is known for the production of corrugated tubes in which thin-wall metal tubes, particularly those which are made from a long strip of sheet metal by continuous deformation to form an open-seam tube, the seam surfaces being then welded together, are deformed into a corrugated tube by an annular corrugator disk which pushes into the circumference of the smooth tube. The corrugating is effected continuously along a helical line with a given depth of corrugation and given pitch in the manner that, within the corrugator head which supports it, the corrugator disk is arranged eccentric to the axis of the tube and inclined at a given angle to it. By the above-described arrangement it is possible to manufacture corrugated tubes in economic fashion. To be sure, only corrugated tubes which have a relatively shallow corrugation can be produced with this device. Such corrugated tubes can be wound on ordinary cable drums and are used, for instance, as sheathing for electric cables, or else as conduits.
If a corrugator disk having a helically extending deforming rib is used in the above-mentioned method, then so-called parallel-corrugated tubes can be produced by this method (Federal Republic of Germany OS No. 1916357).
In order to obtain a deeper corrugation, the corrugation in the aforementioned method has been carried out under axial load in the manner for instance that the metal tube is retarded, as seen in the direction of passage, after the corrugating. Due to the fact that in this method the corrugating tool, i.e. the corrugating disk, is free of forces acting axially on it, a deep corrugation is obtained. However, it has been found that this method leads to difficulties in actual practice, since the application of constant retarding forces--constant retarding forces are indispensable in order to obtain a uniform corrugation--is not possible (Federal Republic of Germany Patent No. 2400842).
The flexible corrugated hoses (metal hoses) obtainable on the market have up to now been produced in discontinuous fashion in that, starting from a length of smooth tube, the corrugation is applied in several passes, the tube being under axial pressure and being pushed together during the corrugation. Longer lengths cannot be produced by this method.